R-744 transcritical refrigeration systems are used in supermarkets to refrigerate or to maintain perishable products in a frozen state, such as foodstuff.
A major disadvantage of a transcritical R-744 refrigeration system is its low energy efficiency ratio (EER) during the warmer periods of the year (critical point 87.761° F.).
When the outside air temperature is such that the R-744 vapors cooled by an exterior heat exchanger (gas cooler) have a temperature higher than the critical point, there will be no condensation. Therefore, in order to obtain a liquid state, the cooled R-744 vapors are fed though a throttling device, thus reducing the pressure and the temperature of the vapors. The result is a mixture of liquid and vapor which, at an ambient temperature of 90° F., will have a ratio of 55% liquid and 45% vapor. It is evident that the mass flow of the compressor in transcritical operation has to be almost doubled in order to obtain the required refrigeration capacity. Hence, there is a necessity for a system and method for increasing the efficiency of an R-744 transcritical refrigeration system.